function randomImg(){
	
	//画像の数
	imgLength = 9;

　//画像の拡張子
	imgExtension = ".jpg";
	
	//画像の保存ディレクトリ
	imgDirectory = "img/top/";
	
	randomInt = Math.random() * imgLength;
	randomInt = Math.ceil(randomInt);
	imgDirectory + randomInt + imgExtension;
	test = document.myImg.src;
	
	document.myImg.src = imgDirectory + randomInt + imgExtension;
}

window.onload = randomImg;